CN107939469B - Continuously variable valve timing driving device and control method - Google Patents
Continuously variable valve timing driving device and control method Download PDFInfo
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- CN107939469B CN107939469B CN201711470232.3A CN201711470232A CN107939469B CN 107939469 B CN107939469 B CN 107939469B CN 201711470232 A CN201711470232 A CN 201711470232A CN 107939469 B CN107939469 B CN 107939469B
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- valve timing
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- 238000000034 method Methods 0.000 title claims description 10
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 28
- 238000007789 sealing Methods 0.000 claims abstract description 28
- 239000010959 steel Substances 0.000 claims abstract description 28
- 238000005096 rolling process Methods 0.000 claims abstract description 5
- 238000002347 injection Methods 0.000 claims description 6
- 239000007924 injection Substances 0.000 claims description 6
- 230000008859 change Effects 0.000 claims description 5
- 239000000945 filler Substances 0.000 claims description 4
- 230000009471 action Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 230000004323 axial length Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
- F01L1/344—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear
- F01L1/34403—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift changing the angular relationship between crankshaft and camshaft, e.g. using helicoidal gear using helically teethed sleeve or gear moving axially between crankshaft and camshaft
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0203—Variable control of intake and exhaust valves
- F02D13/0215—Variable control of intake and exhaust valves changing the valve timing only
- F02D13/0219—Variable control of intake and exhaust valves changing the valve timing only by shifting the phase, i.e. the opening periods of the valves are constant
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
- F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
- F02D13/0261—Controlling the valve overlap
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Valve Device For Special Equipments (AREA)
Abstract
The invention discloses a continuously variable valve timing driving device, comprising: a screw; the sliding nut is sleeved on the screw rod, and a steel ball capable of circularly rolling is arranged between the sliding nut and the screw rod, so that the screw rod rotates relative to the sliding nut when the sliding nut axially moves relative to the screw rod; the both ends fixed connection sealing ring of slip nut, shell body, its coaxial cover is established in the slip nut outside, forms sealedly between the inner wall of shell body and the outer fringe of sealing ring, the shell body includes: a first oil cavity is formed between the first end cover and the sealing check ring of the corresponding sliding nut; a second oil cavity is formed between the second end cover and the corresponding sealing check ring; wherein the sliding nut is axially movably connected with the inner wall of the outer shell; the first oil cavity and the second oil cavity are respectively communicated with the oil supply control system through oil inlets. The continuous variable valve timing driving device provided by the invention has the advantages of simple structure and good stability, and can realize continuous variable valve timing of the intake valve and the exhaust valve.
Description
Technical Field
The invention belongs to the technical field of continuous variable valve timing of an automobile engine, and particularly relates to a continuous variable valve timing driving device and a control method.
Background
The continuously variable valve timing technology of an engine is an important technology in the current automobile engine. Compared with the traditional engine valve mechanism, the engine valve mechanism can not achieve both the fuel economy at low speed and the dynamic property at high speed of the engine, and can only ensure that the engine is in an optimal distribution state in a certain rotating speed range. The continuous variable valve timing technology is to realize the optimal valve timing by continuously changing the early opening or late closing of the intake valve and the exhaust valve of the engine, so that the valve phase always meets the working condition requirement of the engine in an optimal valve distribution state. The continuous variable valve technology utilizes the early opening and early closing of an engine inlet valve to promote the increase of a valve overlap angle so as to improve the exhaust effect, and greatly improve the fuel economy of a low-speed working section of the engine and the torque output of a high-torque working section; the intake valve of the engine can be opened and closed at night, the inertia of air flow is fully utilized to improve the charging efficiency, and the power performance of the engine under high load is greatly ensured. Meanwhile, the continuous variable valve timing technology is also beneficial to improving the instantaneous start-stop performance of the engine of the hybrid electric vehicle.
The existing variable valve timing device in the current market is complex in structure, slow in timing adjustment response and low in precision.
Disclosure of Invention
The invention aims to overcome the defects of complex structure and low adjustment precision of the traditional variable valve timing driving device and provides a continuous variable valve timing driving device which is convenient to install at the end of a cam shaft and has simple structure and higher adjustment precision.
Another object of the present invention is to provide a control method of a continuously variable valve timing driving apparatus capable of controlling the continuously variable valve timing driving apparatus to change the phase of an intake and exhaust camshaft according to the operating condition of an engine, further improving the adjustment accuracy of the continuously variable valve timing driving apparatus.
The technical scheme provided by the invention is as follows:
a continuously variable valve timing driving apparatus comprising:
one end of the screw is coaxially and fixedly connected with an air inlet and outlet cam shaft of the engine, and the other end of the screw is a free end;
the sliding nut is sleeved on the screw, and a steel ball capable of circularly rolling is arranged between the sliding nut and the screw, so that the screw rotates relative to the sliding nut when the sliding nut axially moves relative to the screw; the two ends of the sliding nut are fixedly connected with a sealing check ring,
the shell body, its coaxial cover is established in the slip nut outside, forms sealedly between the inner wall of shell body and the outer fringe of sealing collar, the shell body includes:
the first end cover is rotatably connected to the free end of the screw rod, and a first oil cavity is formed between the first end cover and the sealing check ring of the corresponding sliding nut;
the second end cover is rotatably sleeved at one end of the screw close to the cam shaft and forms a seal with the screw; a second oil cavity is formed between the second end cover and the corresponding sealing check ring;
the driving wheel is coaxially and fixedly connected to the outer wall of the outer shell, and is connected with an engine crankshaft through a driving belt;
the sliding nut is axially movably connected to the inner wall of the outer shell and can synchronously rotate along with the outer shell; the first oil cavity and the second oil cavity are respectively communicated with the oil supply control system through oil inlets.
Preferably, a sliding rail is arranged on the outer side of the sliding nut along the axial direction; and a sliding block matched with the sliding rail is fixedly arranged on the inner wall of the outer shell, and is connected with the outer side of the sliding nut through the sliding block.
Preferably, a spiral groove is arranged between the sliding nut and the screw, the steel ball is arranged in the spiral groove and rolls along the spiral groove, and the screw moment of the spiral groove is as follows:
where F is the axial working load, L is the thread lead, d 0 Is the pitch diameter of the screw, ψ is the thread rise angle at the pitch diameter of the screw, ρ d Is the equivalent friction angle.
Preferably, the center of the first end cover is provided with a positioning shaft sleeve, and the positioning shaft sleeve is connected with the free end of the screw rod.
Preferably, a sealing gasket is adopted to seal between the second end cover and the screw rod.
Preferably, the oil inlet holes of the first oil cavity and the second oil cavity are respectively arranged on the screw rod, and the two oil inlet holes are respectively communicated with the two oil injection holes outside the oil cavity through the oil inlet channel inside the screw rod.
Preferably, the oil filling hole is arranged in an annular groove on the cam shaft.
Preferably, the oil filling hole is connected with an oil supply control system, and the oil supply control system comprises:
an oil pump connected to the oil tank;
an electromagnetic reversing valve which is arranged on an oil supply pipeline of the oil pump, wherein any one of a left channel, a middle channel and a right channel of the reversing valve can be communicated with two oil injection holes;
and the engine ECU is used for controlling the electromagnetic directional valve switching channel according to the working condition of the engine.
Preferably, the oil filling hole is connected with the oil supply control system and further comprises an overflow valve, and the overflow valve is arranged on an oil supply pipeline between the oil pump and the reversing valve.
A control method of a continuously variable valve timing driving apparatus, using the continuously variable valve timing driving apparatus, comprising the steps of:
step one, an engine ECU determines an actually required camshaft phase target value according to feedback signals such as real-time speed, engine speed, cam phase angle and the like of an automobile detected by a sensor;
step two, the engine ECU sends out an instruction to the electromagnetic directional valve according to the required camshaft phase, and controls the electromagnetic directional valve to switch channels; changing the oil flow direction and the oil pressure in the first oil cavity and the second oil cavity, so as to change the sizes of the first oil cavity and the second oil cavity, wherein the oil pushes the sliding nut to slide along the sliding block relative to the screw rod;
step three, when the sliding nut axially slides, a steel ball in the sliding nut rolls and screws on a screw rod, and the screw rod can rotate by a certain circumferential angle relative to the sliding nut; the sliding rail on the outer side of the sliding nut is limited by the sliding block in the outer shell, so that the outer shell and the sliding nut synchronously rotate, and the outer shell and the driving wheel synchronously rotate, so that the cam shaft end screw rod rotates by a certain circumferential angle relative to the driving wheel, and further the rotation of the cam shaft end screw rod in the continuous variable valve timing driving device relative to the driving wheel is realized, and the cam shaft phase adjustment target value is reached.
The beneficial effects of the invention are as follows:
the continuous variable valve timing driving device provided by the invention has the advantages of simple structure and good stability, can be conveniently assembled at one end of the air inlet and outlet cam shaft of the engine to realize the continuous variable valve timing of the air inlet and outlet valve, ensures that the valve opening time is always in an ideal state, gives consideration to different working conditions of low speed and high speed of the engine, and greatly improves the problems of fuel consumption, power output and the like of the engine.
The control method of the continuous variable valve timing driving device provided by the invention can control the continuous variable valve timing driving device to change the phase of the intake and exhaust cam shafts according to the working condition of the engine, and further improves the adjustment precision of the continuous variable valve timing driving device.
Drawings
Fig. 1 is a schematic view showing an external structure of a continuously variable valve timing driving apparatus according to the present invention.
Fig. 2 is a schematic view showing the internal structure of the continuously variable valve timing driving apparatus according to the present invention.
Fig. 3 is a schematic view of a first end cap according to the present invention.
Fig. 4 is a schematic view of the structure of the outer casing according to the present invention.
Fig. 5 is a schematic view of a slip nut according to the present invention.
Fig. 6 is a schematic view showing the installation of a steel ball in the continuously variable valve timing driving apparatus according to the present invention.
Fig. 7 is a schematic diagram of a communication left channel of an electromagnetic directional valve in a continuously variable valve timing driving apparatus according to the present invention.
Fig. 8 is a schematic diagram of a medium position passage in connection with an electromagnetic directional valve in a continuously variable valve timing driving apparatus according to the present invention.
Fig. 9 is a schematic diagram of an electromagnetic directional valve communicating right-hand passage in the continuously variable valve timing driving apparatus according to the present invention.
Fig. 10 is a timing chart of variation in intake valve displacement achieved by the continuously variable valve timing driving apparatus according to the present invention.
Detailed Description
The present invention is described in further detail below with reference to the drawings to enable those skilled in the art to practice the invention by referring to the description.
As shown in fig. 1 to 7, the present invention provides a continuously variable valve timing driving apparatus which is connected to one end of an intake and exhaust camshaft 100 extending outside an engine block, and the other end of the camshaft 100 is a cam gear (not shown) disposed in the engine block. The timing drive apparatus includes: one end of the screw 210 is coaxially and fixedly connected with the air intake and exhaust cam shaft 100 of the engine, and the other end is a free end; the screw 210 in this embodiment is machined based on an extension of the camshaft 100 to meet the assembly strength requirements.
And the sliding nut 220 is sleeved on the screw rod 210, and two ends of the sliding nut 220 are fixedly connected with the sealing check rings 240. In this embodiment, the sliding nut 220 is fixedly connected with the sealing retainer 240 through a screw, a sealing gasket is installed between the sliding nut 220 and the sealing retainer 240, and a sealing gasket is installed between the inner ring of the sealing retainer 240 and the screw 210, so that oil is prevented from entering the position where the sliding nut 220 is located, and the relative rotation between the sliding nut 220 and the screw 210 is not affected.
A steel ball 230 capable of circulating rolling is arranged between the sliding nut 220 and the screw rod, so that the screw rod 210 rotates relative to the sliding nut 220 when the sliding nut 220 axially moves relative to the screw rod 210. The middle part of the screw 220 is processed into a spiral groove 231 matched with the steel ball 230, the sliding nut 220 is internally provided with a spiral groove corresponding to the spiral groove 231, and the steel ball 230 is positioned between the spiral groove 231 and the spiral groove in the sliding nut 220. In order to meet the convenience of assembling and disassembling the steel ball 230 and the assembly requirement between the sliding nut 220 and the inner wall of the outer shell 250, a steel ball guide pipe 221 is arranged at the outer side of the sliding nut 220, and the steel ball 230 is installed at the interfaces 222 at the two ends of the sliding nut 220 and the steel ball guide pipe 221. The steel ball conduit 221 is fixed on the outer wall of the slip nut 220 through a fixing buckle, and the interfaces at the two ends of the steel ball conduit 221 are tangent to the side line of the spiral groove in the slip nut 220, so that the smoothness of continuous rolling of the steel ball 230 in the steel ball conduit 221 and the slip nut 220 is ensured. The steel ball guide 221 connects all the steel balls 230 in the slip nut 220 into a closed continuous circulation loop structure, and the steel balls 230 continuously and smoothly roll in the spiral groove along with the axial slip of the slip nut 220 so as to realize the circumferential rotation of the screw 210 relative to the slip nut 220. Meanwhile, in order to ensure dynamic balance during high-speed rotation of the sliding nut 220, two counterweights 223 corresponding to the steel ball guide pipe 221 are arranged on the outer wall of the sliding nut 220 opposite to the steel ball guide pipe 221.
When the axial length of the spiral groove 231 on the screw rod 210 satisfies that the sliding nut 220 moves axially on the screw rod 210, the spiral groove 231 on the screw rod 210 does not exceed the inner sides of the sealing check rings 240 at two ends of the sliding nut 220, and the axial length of the spiral groove in the sliding nut 220 is smaller than the axial length of the sliding nut 220, so that oil liquid outside the two sealing check rings 240 is prevented from entering the spiral groove.
An outer housing 250 coaxially sleeved outside the slip nut 220, and a gasket is installed between an inner wall of the outer housing and an outer edge of the sealing collar 240 to form a seal, and the outer housing 250 includes: the first end cap 251 is provided at the center thereof with a positioning sleeve 252, and is connected to the free end of the screw 210 through the positioning sleeve 252. The positioning sleeve 252 can support the shaft end of the screw 210, so as to ensure dynamic balance during relative rotation between the screw 210 and the housing 250 and during high-speed rotation of the timing driving device along with the engine crankshaft. The first oil chamber 310 is formed between the first end cap 251 and the sealing collar 240 of its corresponding slip nut 220. The second end cover 253 is rotatably sleeved at one end of the screw 210 close to the cam shaft 100, and a sealing gasket is arranged between the second end cover 253 and the screw 210 to form a seal; the second oil chamber 320 is formed between the second end cap 253 and its corresponding sealing collar 240. The main body of the outer case 250 is assembled with the first end cap 251 and the second end cap 253 by screws, and sealing rings are additionally arranged on the inner sides of the first end cap 251 and the second end cap 253 to ensure the tightness between the main body of the outer case 250 and the first end cap 251 and the second end cap 253. Wherein the slip nut 220 is axially movably connected to the inner wall of the outer housing 250 and can synchronously rotate along with the outer housing 250; in this embodiment, three sliding rails 224 are uniformly arranged on the outer wall of the sliding nut 220 along the axial direction, and each sliding rail 224 is provided with a sliding groove, a sliding block 254 matched with the corresponding sliding rail 224 is fixedly connected on the inner wall of the outer housing 250, and the sliding block 254 is located in the axial middle of the inner wall of the housing 250, so that the sliding nut 220 can only axially slide along the sliding block 254 in the axial direction relative to the outer housing 250, and the sliding nut 220 and the outer housing 250 always synchronously rotate around the axial direction. The length of each slide 254 on the inner wall of the outer housing 250 is such that it meets the slip distance requirement for axial slippage of the slip nut 220, as determined by the phase of the camshaft change required. When the initial position is assembled, the slider 254 is positioned intermediate the slide rails 224.
A driving wheel 260 coaxially and fixedly connected to the outer wall of the outer casing 250, wherein the driving wheel 260 is connected with an engine crankshaft through a driving belt; when the engine crankshaft rotates, the driving wheel 260 is driven to rotate, and the driving wheel 260 can adopt a belt wheel or a chain wheel.
The first oil chamber 310 and the second oil chamber 320 realize the inlet and outlet of oil through an oil inlet 311 and an oil inlet 321 respectively arranged on the screw 210. The oil inlet 311 and 321 are respectively communicated with the oil injection hole 312 and 322 outside the oil chamber through two oil inlet channels inside the screw 210. The oil filler hole 312 and the oil filler hole 322 are connected to an oil supply control system. Preferably, the oil filling holes 312 and 322 are respectively disposed in annular grooves on the camshaft 100, so as to ensure smooth oil supply in the oil path when the timing driving device rotates with the camshaft 100.
As shown in fig. 7 to 9, the oil supply control system is composed of an oil pump 330, an electromagnetic directional valve 340, a relief valve 350, an oil tank 360, an engine ECU, and the like. The continuously variable valve timing driving apparatus keeps the slip nut 220 stationary at the initial position of the screw 210 at the initial start, that is, at the idle operation of the engine, and the medium oil amount of the first oil chamber 310 and the second oil chamber 320 is equal, that is, the oil pressure in the first oil chamber 310 and the second oil chamber 320 is equal.
The invention also provides a control method of the continuous variable valve timing driving device, and in the running process of the automobile, the engine ECU calculates the actual required camshaft phase according to feedback signals of the real-time speed, the engine rotating speed, the cam phase angle and the like of the automobile detected by the sensor. The engine ECU sends an instruction to the electromagnetic directional valve 340 according to the actually required camshaft phase, changes the valve core position in the directional valve, controls the left, middle and right channels of the electromagnetic directional valve 340 to be respectively communicated with the oil filling hole 312 and the oil filling hole 322 on the camshaft 100 through oil ways, and further changes the oil flow direction and the oil pressure in the first oil cavity 310 and the second oil cavity 320, thereby changing the sizes of the first oil cavity 310 and the second oil cavity 320, pushing the sliding nut 220 to axially move so as to realize the relative rotation of the sliding nut 220 and the screw 210, and further realizes the rotation of the screw 210 at the camshaft end in the continuously variable valve timing driving device relative to the driving wheel 260, so as to realize the phase adjustment of the camshaft.
As shown in fig. 7, when the left channel 341 of the electromagnetic directional valve 340 is connected to the oil filling hole 312 and the oil filling hole 322, respectively, the oil in the oil tank 360 is filled into the first oil chamber 310 through the oil passage 370 under the action of the oil pump 330. As the amount and pressure of the oil increases, the oil in the first oil chamber 310 pushes the slip nut 220 to slip along the slider 254 relative to the screw 210 toward the second oil chamber 320, and the sealing ring 240 of the second oil chamber 320 pushes the oil in the second oil chamber 320 to flow back into the oil tank 360 through the oil passage 380.
When the sliding nut 220 slides toward the camshaft 110 (in the direction of the second oil chamber 320), the steel ball 230 in the sliding nut 220 rolls and screws rightward on the screw 210, and the sliding nut 220 and the screw 210 rotate by a certain circumferential angle. Because the slide rail 224 outside the slip nut 220 is limited by the slide block 254 in the outer housing 250, the outer housing 250 and the slip nut 220 rotate synchronously, and the outer housing 250 and the driving wheel 260 rotate synchronously, the cam shaft end screw 210 rotates by a certain circumferential angle relative to the driving wheel 260. The length of the sliding distance of the sliding nut 220 determines the circumferential angle through which the screw 210 rotates.
As shown in fig. 9, when the right channel 343 of the electromagnetic directional valve 340 is respectively connected to the oil filling hole 312 and the oil filling hole 322, the oil in the oil tank 360 is introduced into the second chamber 320 through the oil passage 380 under the action of the oil pump 330, and the oil in the second chamber 320 pushes the sliding nut 220 to slide along the sliding block 254 relative to the screw 210 toward the first chamber 310 due to the increase of the oil volume and the oil pressure. The sealing collar 240 of the first oil chamber 310 pushes the oil in the first oil chamber 310 to flow back into the oil tank 360 through the oil passage 370.
When the sliding nut 220 slides in a direction away from the camshaft 110 (in the direction of the first oil chamber 310), the steel ball 230 in the sliding nut 220 rolls and screws leftwards on the screw 210, and a certain circumferential angle is formed between the sliding nut 220 and the screw 210. Because the slide rail 224 outside the slip nut 220 is limited by the slide block 254 in the outer housing 250, the outer housing 250 and the slip nut 220 rotate synchronously, and the outer housing 250 and the driving wheel 260 rotate synchronously, the cam shaft end screw 210 rotates by a certain circumferential angle relative to the driving wheel 260. The length of the sliding distance of the sliding nut 220 determines the circumferential angle through which the screw 210 rotates.
When the camshaft phase is adjusted to the position required by the actual working condition of the engine, the sliding nut 220 slides to the corresponding designated position under the action of oil pressure, the engine ECU timely controls the electromagnetic directional valve 340 to switch to the middle position channel 342 (as shown in fig. 8) according to the feedback information, at this time, the oil pressure in the left oil chamber 203 and the right oil chamber 204 is equal, and the sliding nut 220 is kept relatively stationary on the screw 210. If the oil pressure in the oil chamber corresponding to the oil pump exceeds the predetermined oil pressure before the electromagnetic directional valve 340 is switched to the neutral position, the system opens the relief valve 350 to perform balance protection until the oil pressures in the oil chambers on the left and right sides are equal.
The continuously variable valve timing driving apparatus converts linear sliding movement of the sliding nut 220 into rotational movement of the screw 210 using a reverse transmission effect of ball screw transmission. In the present embodiment, the torque of the spiral groove (i.e., the thread torque) between the screw 210 and the slip nut 220 satisfies the following formula M' to optimize the reverse transmission efficiency of the ball screw transmission.
Where F is the axial working load, L is the thread lead, d 0 Is the pitch diameter of the screw, ψ is the thread rise angle at the pitch diameter of the screw, ρ d Is the equivalent friction angle (usually taken as ρ d ＝tg -1 0.0035)。
The specific adjustment process of the continuously variable valve timing drive apparatus will be further described by way of example:
in one embodiment, with reference to the direction of rotation of the drive wheel 260 shown in FIG. 1, the camshaft 100 acts as an intake camshaft. As shown in fig. 7, when the left channel 341 of the electromagnetic directional valve 340 is connected to the oil filling hole 312 and the oil filling hole 322, respectively, when the sliding nut 220 slides towards the camshaft 110 under the action of oil pressure, the steel ball 230 in the sliding nut 220 rolls and screws on the screw 210 to the right, and a certain circumferential angle is rotated between the sliding nut 220 and the screw 210 (the sliding distance of the sliding nut 220 determines the size of the circumferential angle rotated by the screw 210), so that the camshaft 100 lags behind a certain circumferential angle relative to the driving wheel 260, namely, the phase of the intake cam lags, thereby realizing delayed opening and closing of the intake valve, improving the charging efficiency and providing guarantee for the high rotation speed and high power working section of the engine.
In another embodiment, with reference to the direction of rotation of the drive wheel 260 shown in fig. 1, the camshaft 100 acts as an intake camshaft. As shown in fig. 9, when the right channel of the electromagnetic directional valve 340 is respectively provided with the oil filling hole 312 and the oil filling hole 322, and the sliding nut 220 slides in a direction away from the camshaft 110 under the action of oil and oil pressure, the steel ball 230 in the sliding nut 220 rolls and screws leftwards on the screw 210, and a certain circumferential angle is rotated between the sliding nut 220 and the screw 210, so that the camshaft 100 advances by a certain circumferential angle relative to the driving wheel 260, that is, the phase of the intake cam is advanced, so that the intake valve is opened and closed in advance, the valve overlap angle is increased, the exhaust effect is improved, and the fuel economy of the low-rotation-speed working section of the engine and the torque output of the high-torque working section of the engine are improved.
The continuously variable valve timing driving device realizes the continuous variation of the intake and exhaust valve phases by controlling the left and right sliding distance of the sliding nut 220 on the screw 210, and the corresponding intake valve displacement variation timing curve is shown in fig. 10.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.
Claims (8)
1. A continuously variable valve timing driving apparatus, characterized by comprising:
one end of the screw is coaxially and fixedly connected with an air inlet and outlet cam shaft of the engine, and the other end of the screw is a free end; the screw is processed based on the extension part of the cam shaft;
the sliding nut is sleeved on the screw, and a steel ball capable of circularly rolling is arranged between the sliding nut and the screw, so that the screw rotates relative to the sliding nut when the sliding nut axially moves relative to the screw; the two ends of the sliding nut are fixedly connected with a sealing check ring;
the shell body, its coaxial cover is established in the slip nut outside, forms sealedly between the inner wall of shell body and the outer fringe of sealing collar, the shell body includes:
a first end cap rotatably connected to the free end of the screw, the first end cap and its corresponding sealing collar forming a first oil chamber therebetween;
the second end cover is rotatably sleeved at one end of the screw close to the cam shaft and forms a seal with the screw; a second oil cavity is formed between the second end cover and the corresponding sealing check ring;
the driving wheel is coaxially and fixedly connected to the outer wall of the outer shell, and is connected with an engine crankshaft through a driving belt;
the sliding nut is axially movably connected to the inner wall of the outer shell and can synchronously rotate along with the outer shell; the first oil cavity and the second oil cavity are respectively communicated with the oil supply control system through oil inlets;
a sliding rail is arranged on the outer side of the sliding nut along the axial direction; a sliding block matched with the sliding rail is fixedly arranged on the inner wall of the outer shell and is connected with the outer side of the sliding nut through the sliding block;
a spiral groove is formed between the sliding nut and the screw, the steel ball is arranged in the spiral groove and rolls along the spiral groove, and the screw moment of the spiral groove is as follows:
where F is the axial working load, L is the thread lead,is the middle diameter of the screw rod>Is the thread lead angle at the pitch diameter of the screw,is the equivalent friction angle.
2. The continuously variable valve timing driving apparatus according to claim 1, wherein the first end cap is provided with a positioning boss at a center thereof, and is connected with a free end of the screw through the positioning boss.
3. The continuously variable valve timing driving apparatus according to claim 2, wherein a gasket seal is employed between the second end cap and the screw.
4. The continuously variable valve timing driving apparatus according to claim 1 or 2, wherein the oil inlet holes of the first oil chamber and the second oil chamber are provided on the screw respectively, and the two oil inlet holes are communicated with the two oil filler holes outside the oil chamber through the oil inlet passage inside the screw respectively.
5. The continuously variable valve timing driving apparatus according to claim 4, wherein the oil filler hole is provided in an annular groove on a camshaft.
6. The continuously variable valve timing driving apparatus according to claim 5, wherein the oil injection hole is connected to an oil supply control system, the oil supply control system comprising:
an oil pump connected to the oil tank;
an electromagnetic reversing valve which is arranged on an oil supply pipeline of the oil pump, wherein any one of a left channel, a middle channel and a right channel of the reversing valve can be communicated with two oil injection holes;
and the engine ECU is used for controlling the electromagnetic directional valve switching channel according to the working condition of the engine.
7. The continuously variable valve timing driving apparatus according to claim 6, wherein the oil injection hole is connected to an oil supply control system further comprising a relief valve provided on an oil supply line between the oil pump and a reversing valve.
8. A control method of a continuously variable valve timing driving apparatus using the continuously variable valve timing driving apparatus according to any one of claims 1 to 7, characterized by comprising the steps of:
step one, an engine ECU determines an actually required camshaft phase target value according to feedback signals such as real-time speed, engine speed, cam phase angle and the like of an automobile detected by a sensor;
step two, the engine ECU sends out an instruction to the electromagnetic directional valve according to the required camshaft phase, and controls the electromagnetic directional valve to switch channels; changing the oil flow direction and the oil pressure in the first oil cavity and the second oil cavity, so as to change the sizes of the first oil cavity and the second oil cavity, wherein the oil pushes the sliding nut to slide along the sliding block relative to the screw rod;
step three, when the sliding nut axially slides, a steel ball in the sliding nut rolls and screws on a screw rod, and the screw rod can rotate by a certain circumferential angle relative to the sliding nut; the sliding rail on the outer side of the sliding nut is limited by the sliding block in the outer shell, so that the outer shell and the sliding nut synchronously rotate, and the outer shell and the driving wheel synchronously rotate, so that the cam shaft end screw rod rotates by a certain circumferential angle relative to the driving wheel, and further the rotation of the cam shaft end screw rod in the continuous variable valve timing driving device relative to the driving wheel is realized, and the cam shaft phase adjustment target value is reached.
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